French terry
Loopback terry with the inside loops sheared and brushed for warmth and softness. Heavier and warmer than loopback; less defined surface.
French terry starts as loopback terry — same loop-pile knit construction — and gets the inside loops sheared, brushed, or both. The result is fluffier, warmer, and softer against the skin, but heavier and harder to dry. It's what most people associate with the word "fleece" in casualwear.
In winter-weight sweatshirts (18–20 oz) the brushed inside is a defining feature. In lighter pieces it's often just called "terry" without the loopback distinction. The shorthand: if the inside feels like a towel, it's loopback. If it feels like a stuffed animal, it's french terry / fleece.
GSM
Grams per square meter — the standard unit for fabric weight. Higher GSM = heavier, denser, often more durable.
Loopback terry
A knit fabric with smooth jersey on the outside and uncut yarn loops on the inside. The classic sweatshirt construction.
Pilling
Small balls of tangled fibers that form on fabric surfaces from friction. Tells you about fiber quality, knit construction, and how the garment was made.